Deepwater containment systems with flexible riser and methods of using same

ABSTRACT

A subsea oil containment system, comprising: a subsea collector located near the bottom of a body of water; a surface collector located near a surface of the body of water; and a flexible riser connected to the subsea collector at a first end and extending to a second end located near the surface collector.

This application claims the benefit of U.S. Provisional Application No.61/376,595 filed Aug. 24, 2010, the entire disclosure of which is herebyincorporated by reference.

BACKGROUND

When oil and gas is spilled into the sea, for example from a leakingtanker ship, a leaking pipeline, from oil seeping from an undergroundformation, or from oil flowing from a subsea wellhead or blowoutpreventer, there is a desire to collect the oil and gas and contain andtransport or otherwise dispose of the oil and gas to preventenvironmental damage to the sea and nearby coastlines. Various systemsand methods of collecting spilled oil and gas are known in the art andset forth below:

U.S. Pat. No. 4,405,258 discloses a method for storing alighter-than-water fluid, e.g., oil, produced from the blowout of anoffshore subsea well. The method includes the steps of deploying acontainment dome in shallow water near the location of the seabed wherethe containment dome is to be located. The containment dome as an upperexpanded dome-like fluid impervious membrane, a fluid impervious hollowperipheral ring attached to the periphery of the membrane to provide adepending bag-like container, and discrete water drainage means withinthe bag-like container for connection to pump conduit means therefrom.Wet sand from the seabed is then pumped into the bag-like container, andwater is then drained from the wet sand through the water drainage meansso as to provide a body of drained sand disposed within the bag-likecontainer and providing a hollow peripheral ring as a hollow peripheraltorus acting as a self-supporting structure and as an anchor for thedome-like structural unit. The dome is then charged with a buoyantamount of air and the buoyed dome is floated out to the site where thedome is to be deployed. It is then submerged by controllably releasingthe air while substantially simultaneously filling the dome with water,thereby sinking the dome until the lighter-than-water fluid is capturedwithin the dome, while such fluid substantially simultaneously displaceswater from within the dome. U.S. Pat. No. 4,405,258 is hereinincorporated by reference in its entirety.

U.S. Pat. No. 4,643,612 discloses an oil storage barge having a concavebottom is adapted to be anchored over a subsea well or pipeline that isleaking oil. Flexible skirts extend to the ocean floor, and oil that istrapped under the barge may be stored in the barge or then transferredto another vessel. U.S. Pat. No. 4,643,612 is herein incorporated byreference in its entirety.

U.S. Pat. No. 5,114,273 discloses a protective device installed to oraround an offshore drilling platform for oil or gas and the device whenin operation to encircle or enclose the platform with a floatingcontainment device and attached oil containment curtain hanging from thedevice to the ocean floor. The pollution containment device to besubmerged normally and activated to the surface when needed. This devicewill entrap offshore platform pollutants in a short amount of time witha minimum amount of effort and will maintain a clean environment. Othermethods of offshore platform pollution containment devices are shown,including permanent non-moving oil pollution containment barriers andactivated barriers that operate internally and externally of the oilplatform to form an all encompassing barrier from the ocean floor toabove the water surface to hold an oil spill to the platform area. U.S.Pat. No. 5,114,273 is herein incorporated by reference in its entirety.

U.S. Pat. No. 5,213,444 discloses an oil/gas collector/separator forrecovery of oil leaking, for example, from an offshore or underwater oilwell. The separator is floated over the point of the leak and tetheredin place so as to receive oil/gas floating, or forced under pressure,toward the water surface from either a broken or leaking oil wellcasing, line, or sunken ship. The separator is provided with adownwardly extending skirt to contain the oil/gas which floats or isforced upward into a dome wherein the gas is separated from theoil/water, with the gas being flared (burned) at the top of the dome,and the oil is separated from water and pumped to a point of use. Sincethe density of oil is less than that of water it can be easily separatedfrom any water entering the dome. U.S. Pat. No. 5,213,444 is hereinincorporated by reference in its entirety.

U.S. Pat. No. 6,592,299 discloses a method of detecting and locatingfresh water springs at sea essentially by taking salinity measurementsand by methods and installations for collecting the fresh water. Thecollection installations comprise an immersed bell-shaped reservoircontaining and trapping the fresh water in its top portion, and apumping system for taking fresh water and delivering the fresh water viaa delivery pipe, characterized in that the circumference of the bottomend of the reservoir and/or the circumference of the bottom end of achimney inside the reservoir and open at its top end and surrounding thefresh water resurgence in part and preferably in full, follow(s) closelythe outline of the relief of the bottom of the sea so as to provideleakproofing between the circumference(s) and the bottom of the sea.U.S. Pat. No. 6,592,299 is herein incorporated by reference in itsentirety.

There is a need in the art for one or more of the following:

Improved systems and methods for collecting spilled oil and gas from amarine environment;

Improved systems and methods for collecting oil and gas spilling from asubsea well;

Improved systems and methods for collecting oil and gas spilling from asubsurface formation located beneath a body of water; and/or

Improved systems and methods for collecting oil and gas spilling from asubsurface formation located beneath a body of water, and then burningthe gas and containing the oil in a surface vessel.

SUMMARY OF THE INVENTION

One aspect of the invention provides a subsea oil containment system,comprising a subsea collector located near a bottom of a body of water;a surface collector located near a surface of the body of water; and aflexible riser connected to the subsea collector at a first end andextending to a second end located near the surface collector.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the features and advantages of the present invention can beunderstood in detail, a more particular description of the invention maybe had by reference to the embodiments thereof that are illustrated inthe appended drawings. These drawings are used to illustrate onlytypical embodiments of this invention, and are not to be consideredlimiting of its scope, for the invention may admit to other equallyeffective embodiments. The figures are not necessarily to scale andcertain features and certain views of the figures may be shownexaggerated in scale or in schematic in the interest of clarity andconciseness.

FIG. 1 is a schematic diagram depicting a wellsite positioned about asubsea reservoir, the wellsite having a containment system in accordancewith an aspect of the present invention.

FIG. 2A is a schematic diagram depicting a wellsite positioned about asubsea reservoir, the wellsite having a containment system with aflexible riser in accordance with an aspect of the present invention.

FIG. 2B is a schematic diagram depicting a portion 2B of the flexibleriser of FIG. 2A.

FIG. 3A is a cross-sectional view of the flexible riser of FIG. 2A takenalong line 3A-3A, the flexible riser having a riser support.

FIG. 3B is a cross-sectional view of the flexible riser of FIG. 3A withmultiple riser supports.

FIG. 4 is a flow chart depicting a method of deepwater containment.

DETAILED DESCRIPTION

Presently preferred embodiments of the invention are shown in theabove-identified figures and described in detail below. Embodiments aredescribed with reference to certain features and techniques forcontaining fluids released into the sea.

FIG. 1:

FIG. 1 is a schematic diagram depicting a wellsite 100 positioned abouta subsea reservoir 102. The wellsite 100 is provided with a containmentsystem 101 for capturing fluids released into the sea 103. Preferably,the containment system 101 and each of its components are configured foroperability in harsh conditions and/or are transportable as needed.

The wellsite 100 includes a surface collector 104 floating on the sea103, with a flexible riser 106 extending therebelow for receiving fluidsgenerated from the reservoir 102. A subsea end of the flexible riser 106is positioned above a blow out preventer (BOP) 112 positioned on the seafloor (or mud line) 110. The BOP 112 is positioned above a wellbore 114that extends through the subsea floor 110 and into the reservoir 102.The BOP 112 is in fluid communication with the wellbore 114 forreceiving the fluids (e.g., gas, hydrocarbons, water, etc.) from thereservoir 102.

From time to time, fluid from the reservoir 102 may escape into the sea103. In some cases, a leak 130 may allow fluid to escape from thewellsite system 100 and into the sea 103 as fluid is produced from thereservoir 102. In such cases, the containment system 101 may be employedto re-capture fluid released by one or more leaks 130.

As shown in FIG. 1, the subsea containment system 101 includes theflexible riser 106 positioned above the BOP 112 for receiving fluidstherefrom. The flexible riser 106 preferably shifts with movement of thesea 103 that may result from, for example, currents, waves, storms, etc.The flexible riser 106 allows fluid to naturally flow from the BOP 112to the surface, for example due to buoyancy of the oil and/or gas in thewater. The fluids received by the flexible riser 106 are passed throughthe riser 106 and to the surface collector 104 as will be described morefully herein.

Fluid drawn from the reservoir 102 and to the surface via riser 106 maybe stored in the surface collector 104. The surface collector 104 maybe, for example, a separator that separates components of the fluid,such as gas and liquid. The portions of the fluid stored in the surfacecollector 104 may optionally be removed, for example, by burning the gaswith a flare 124 or by allowing the gas to escape into the atmosphere.Preferably, the pressure of the fluid is reduced in the surfacecollector 104. The remaining fluid may be passed to a vessel 120 viatubing (or hoses, floating line or off-take lines) 126 for transport,for example with a pump. The tubing 126 preferably fluidly connects thesurface collector 104 to the vessel 120 for establishing fluidcommunication therebetween.

FIGS. 2A & 2B:

FIGS. 2A and 2B are schematic diagrams depicting a wellsite 200 having acontainment system 201. The containment system 201 is provided with aflexible riser 206 and a surface collector 204 that may operate in thesame manner as the flexible riser 106 and the surface collector 104,respectively, of FIG. 1. A BOP 212 may also be provided for passingfluid from a reservoir 202 via a wellbore 214 in the same manner as theBOP 112 of FIG. 1.

The flexible riser 206 is positioned over BOP 212 such that a leak 230from BOP 212 (or a leak from another location) may be collected therein.Fluid passing from the BOP 212 flows into the flexible riser 206. Afunnel or other subsea collector (not shown) may optionally bepositioned about the subsea end of the flexible riser 206 to facilitateflow into the flexible riser 206. The flexible riser 206 is preferablyconfigured to capture the fluid leaking from the BOP 212 to preventpassage of the fluid into the sea 203.

A subsea end of the flexible riser 206 is secured to sea floor 210 bymooring lines 233 a anchored with clump weights 234 a, suction piles, orother anchoring systems as are known in the art. Clump weights andmooring lines as described herein may employ, for example, conventionalmooring systems. Preferably, the flexible riser 206 is secured intoposition using multiple weights positioned about the BOP 212. Theflexible riser 206 is preferably secured in a detached position at about5 to 15 m above the sea floor 210, depending on the height of BOP 212.This detached position is preferably provided to enable access to theBOP 212, for example by an ROV (not shown).

The flexible riser 206 extends a distance above the BOP 212 and up to ornear to the surface collector 204 for passing fluid therebetween. Theflexible riser 206 may be substantially vertical as shown in FIG. 1, orat an angle as shown in FIG. 2A. The flexible riser 206 is preferablypositioned to enable natural flow of fluid from the leak 230 about theBOP 212 and through the flexible riser 206. Specific weights of thefluids (e.g., oil, gas, water) naturally flow within a water-continuousenclosed column extending through the flexible riser 206.

The flexible riser 206 is preferably a free standing, buoyed riser. Theflexible riser 206 may be made of a flexible and/or repairable material,such as fabric, polymer and/or other material sufficiently flexible andwater tight to enable the passage of fluid. The flexible material mayalso have a sufficient strength (e.g., about 1000N/cm) to handle hightemperature, high pressure, high density, corrosive and/or other fluidsproduces from the subsea reservoir 202. Preferably, the flexible riser206 is sufficiently flexible to move with the movement of the sea 203,while maintaining sufficient rigidity to permit the passage of fluidbetween the BOP 212 and the surface collector 204.

As shown in greater detail in FIG. 2B, the flexible riser 206 has aflexible tube 236 and at least one riser support 237. The riser support237 may include tube rings 238, a wire 242, link rings 244 and a supportcable 246. A plurality of the tube rings 238 are spaced apart andpositioned at various depths along the flexible tube 236 for providingsupport thereto. Preferably, the tube rings 238 are circular membersthat maintain an opening through the flexible tube 236 to facilitate thepassage of fluid therethrough. The opening through the flexible tube 236is preferably of a large diameter (e.g., from about 3 meters to about 20meters, for example from about 5 to about 10 meters). The tube rings 238may be integral with the flexible tube 236 (e.g., woven into theflexible tube), or attached on an inside or outside surface of theflexible tube 236.

The wire 242 and/or support cable 246 extend between the subsea floor210 and the surface collector 204 for providing support to the flexibleriser 206. As shown, the wire 242 and support cable 246 are secured tothe subsea floor 210 by clump weights 234 c. The wire 242 and/or supportcable 246 are secured to the flexible riser 206 by the link rings 244.The link rings 244 may be secured to the flexible tube 236 and/or thetube rings 238. The same and/or separate link rings 244 may support thewire 242 and the support cable 246. Preferably, the link rings 244 aresecured to the flexible tube 236 with the wire 242 and/or support cable246 therethrough. In this configuration, the wire 242 and support cable246 are free to move through the link rings 244 as the flexible tube 236moves. Wire 242 and support cable 246 are preferably positioned along anouter surface of the flexible tube 236 via the link rings 244 to provideindependent movement of the wire 242, support cable 246 and flexibletube 236.

FIGS. 3A & 3B:

As shown in the cross-sectional views of FIGS. 3A and 3B, one or moreriser supports 237 may be positioned about the flexible tube 236. Linkrings 244 may be positioned at intervals about the flexible tube 236 toreceive the wires 242 and support cables 246. Preferably, as shown inFIG. 3B, three riser supports 237 are provided about the flexible tube236 at three locations 120 degrees apart. However, it will beappreciated by one of skill in the art that one or more sets of risersupports 237, tube rings 238, link rings 244, wires 242 and/or supportcables 246 may be provided at various locations about the flexible tube236 as desired.

Referring back to FIG. 2A, a surface end of the flexible riser 206extends into the surface collector 204 for passing fluid thereto. Thesurface end of the flexible riser 206 is secured within the surfacecollector by a buoy 248. The buoy 248 has an arm 250 extending therefromwith a support line 233 b hanging therefrom for supporting the flexibletube 206. The support line 233 b may be, for example, a steel cableintegral with the cable 246 and/or wire 242. The buoy 248 may have anadditional support line 233 c extending therefrom for providing furthersupport to the flexible riser 206. The additional support line 233 c ispreferably positioned along the flexible riser 206 between the surfaceand subsea ends of the flexible riser 206. The support lines 233 band/or 233 c may be linked, for example, to one or more link rings 244secured to the flexible tube 236. Support lines 233 d may also beprovided to anchor the flexible riser 206 to the subsea floor 210. Clumpweights 234 b may be provided to secure the flexible riser 206 to thesubsea floor 210.

The support line 233 b preferably extends through the surface collector204 to support the upper end of the flexible riser 206 therein. Thesurface collector 204 may be a conventional surface collector orfloating storage for receiving fluids at the surface. As shown in FIG.2A (partially in cross-section), the surface collector 204 is acylindrically-shaped storage container or floating fence having an openbottom and open top in a ‘donut’ or ‘ring’ configuration. However, thesurface collector 204 may be of a variety of shapes or sizes suitablefor collection and/or separation of fluid received from the flexibleriser 206. The surface collector 204 may be configured to facilitatereceipt, separation and/or transfer of the fluids generated from theleak 230. The surface collector 204 is preferably a gravitationalseparator capable of separating the fluid into, for example, gas andliquids.

A transfer hose 254 may be a floating hose for establishing fluidcommunication between the surface collector 204 and a vessel 220. A pump252 may also be provided for pumping fluid from the surface collector204, through the transfer hose 254 and to the vessel 220 for transport.One or more pumps, supply lines, exhausts, tubings, ports and/or otherdevices may be provided to generate the desired offloading rate. Also,one or more vessels 220 may be used in series and/or parallel.

FIG. 4:

FIG. 4 is a flow chart depicting a method 400 of containment. The method400 may involve positioning 470 a containment system over a BOP at awellsite. The positioning may involve deploying at least a portion ofthe containment system (e.g., 101, 201) to a wellsite (e.g., 100, 200),installing the containment system (e.g., 101, 201) about a BOP (e.g.,112, 212), and removing the containment system.

The method further involves supporting 472 a flexible riser of thecontainment system (e.g., 101, 201) in position between the BOP (e.g.,112, 212) and a surface collector (e.g, 104, 204). The supporting 472may involve mooring 474 the flexible riser (e.g., 106, 206) to a subseafloor about the BOP, mooring 476 the flexible riser in position aboutthe surface collector, positioning 478 tube rings (e.g., 238) about aflexible tube (e.g., 248) of the flexible riser for providing supportthereto, and/or linking 480 at least one support cable (e.g., 246) alongan outer surface of the flexible tube for providing flexible supportthereto.

The method may also involve passing 482 the fluid from the BOP (e.g.,112, 212) to the surface collector (e.g., 204) via the flexible riser(e.g., 106, 206), separating 484 the fluid in the surface collector(e.g., 204) and passing 486 at least a portion of the fluid from thesurface collector (e.g., 204) to a vessel (e.g., 120, 220). In somecases, the flexible riser (e.g., 106, 206) may be secured about thesurface collector (e.g., 204) with a buoy (e.g., 248). The flexibleriser (e.g., 106, 206) may also be secured about the BOP (e.g., 112,212) with lines (e.g., 233 a-d) and weights (e.g., 254). The vessels(e.g., 120, 220) may be an ROV vessel for deploying an ROV (not shown)to the wellsite for activation thereof. The steps of the method may beperformed in any order, and repeated as desired.

In some embodiments, riser 106 and/or 206 may be made of a flexiblesheet material, such as woven polyester, fiber reinforced plastic,polymer sheet such as polyethylene or polypropylene or copolymers, nylonfabric, Dacron fabric, aramid fabric, zylon fabric, or vectran fabric.

It will be understood from the foregoing description that variousmodifications and changes may be made in the preferred and alternativeembodiments of the present invention without departing from its truespirit. For example, the flexible riser may optionally be provided withdevices, such as valves, ports, chokes (not shown) or other devices asdesired.

This description is intended for purposes of illustration only andshould not be construed in a limiting sense. The scope of this inventionshould be determined only by the language of the claims that follow. Theterm “comprising” within the claims is intended to mean “including atleast” such that the recited listing of elements in a claim are an opengroup. “A,” “an” and other singular terms are intended to include theplural forms thereof unless specifically excluded.

1. A subsea oil containment system, comprising: a subsea collectorlocated near a bottom of a body of water; a surface collector locatednear a surface of the body of water; and a flexible riser connected tothe subsea collector at a first end and extending to a second endlocated near the surface collector.
 2. The system of claim 1, whereinthe subsea collector comprises a containment cap located over a sourceof oil located on the bottom of the body of water.
 3. The system ofclaim 1, wherein the subsea collector comprises a containment cap opento a blow out preventer (BOP) and the body of water.
 4. The system ofclaim 1, wherein the subsea collector is anchored to the bottom of thebody of water with one or more clump weights and/or piles.
 5. The systemof claim 1, further comprising a diffuser connected to the second end ofthe riser.
 6. The system of claim 1, wherein the surface collectorcomprises an open bottom surface, the open bottom surface located abovethe second end of the riser.
 7. The system of claim 1, wherein thesurface collector comprises a sealed top surface, the surface collectorcomprising a first outlet for gases near a top of the collector, andcomprising a second outlet for liquids near a bottom of the collector.8. The system of claim 1, wherein the surface collector comprises asealed top surface, the surface collector comprising a first outlet forgases near a top of the collector, and comprising a flare connected tothe first outlet.
 9. The system of claim 1, wherein the surfacecollector comprises a sealed top surface, wherein the top surface of thesurface collector is submerged in the body of water at a depth fromabout 20 to about 60 meters.
 10. The system of claim 1, wherein thesurface collector comprises an open top surface, wherein the open topsurface comprises a first outlet for gases, and comprising a secondoutlet for liquids near a bottom of the collector.
 11. The system ofclaim 1, further comprising a vessel fluidly connected to the surfacecollector by a hose, the vessel adapted to store and/or transport atleast a portion of liquids in the surface collector.
 12. The system ofclaim 11, the surface collector further comprising a pump connected tothe hose.